Merge all role-dispatcher pages into single files; add FileBrowser with file-type icons

- DashboardPage, Projects, RequestsPage, ProjectDetailPage, RequestDetail: each now handles team/external/client in one file via role flags — removed 10 old role-specific sub-files
- Layout: client Company nav link goes directly to /company/:id when user has a single company
- FileBrowser: replace emoji icons with colored extension-text badges (square); folder icon stays 📁; Adobe/Figma/design-tool colors for design files
- CompaniesPage: merged team Companies + client company routing (single-company redirect, multi-company list)
- FileSharing: integrated FileBrowser component
- Removed: seafile API + lib, old ServerStatus, TaskDetail, role-split page files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/Login.jsx

@@ -14,7 +14,7 @@ export default function Login() {
 
   useEffect(() => {
     if (currentUser) {
-      navigate(currentUser.role === 'client' ? '/my-dashboard' : '/dashboard', { replace: true });
+      navigate('/dashboard', { replace: true });
     }
   }, [currentUser, navigate]);